The present invention is concerned with a method for transfer of fiber material from one circuit of circulating liquid to another, where the fiber material is transported by circuits positioned at right angles to the axis of rotation of a rotary feed valve and the circulating liquids for effecting transport of the fiber material are screened off through self-cleaning screens located in the feed valve housing, and where the fiber material is transported into and out of the feed valve by circulating liquids that are screened off through self-cleaning screens.
When feeding cellulosic fiber material and liquid into a pressurized treatment vessel, preferably of continuously operating type, such as a digester for pulp making, it is a known practice to use feed valves for transferring the material. The method of transfer is such that the feed valve rotor, being provided with one or more pockets, is brought into various positions in which the pocket or pockets communicate with circulation lines between different treatment vessels.
The purpose of the present invention is to make available an improved method for transferring fiber material between the circulation lines, thereby obtaining improved means of control, more even and less temperature-sensitive feed of the fiber material, lower energy requirement, a final product, such as pulp, of more even quality, and higher pulp yield. The invention also permits more variation in the nature of the raw materials; for example, larger amounts of sawdust and of green chips can be used in the cooking process without causing trouble in the feed system.